Support Python 3.12 + PEP 695 (type statement, new type parameter syntax)

[brentyi]

• Add Python 3.12 to CI + pyproject.toml
• Add example for Python 3.12-style generics
• Add support for type statement

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.89%. Comparing base (b43c668) to head (43ac008).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #135   +/-   ##
=======================================
  Coverage   99.89%   99.89%           
=======================================
  Files          24       24           
  Lines        1943     1945    +2     
=======================================
+ Hits         1941     1943    +2     
  Misses          2        2           

Flag	Coverage Δ
unittests	99.89% <100.00%> (+<0.01%)	⬆️

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